Role of climate anomalies on decadal variation in the occurrence of wintertime haze in the Yangtze River Delta, China

The wintertime haze day (HD) in the Yangtze River Delta (YRD) region of China shows significant upward trend during the past decades due to the rapid industrialization and urbanization. Besides the enhanced anthropogenic emission, climate change also plays the important role on the long term HD variations. This study suggests that the warming anomaly in the lower and middle troposphere over the continent around YRD in recent decade affects the decadal variation of wintertime HD with two aspects. First, reversing the zonal thermal difference crosses YRD to stimulate anomalous southerlies leading to reduced seasonal prevailing north wind. Secondly, developing the deep inversion below the mid-troposphere to enhance the atmospheric stability. As a result of the response to the thermal anomaly, more frequent and persistent air stagnations in recent decade are expected to result in the reduction for the atmospheric horizontal dispersion and the vertical diffusion capacity leading to more occurrence of wintertime HD in YRD.268